1. Technical Field
The present invention relates to a printing system, a printing system control program and a printing system control method used for a facsimile apparatus or a copying machine and OA system, and particularly to the printing system, the printing system control program and printing system control method, and print data generating system, print data generating program and print data generating method eminently suitable for drawing predetermined characters and images by discharging micro-particulates of liquid ink with a plurality of colors onto printing papers (recording materials), that is, for performing ink-jet print processing.
2. Related Art
Herewith, there is a description of a printing system, particularly, the printing system adopting an ink-jet printer (hereinafter, referred to as “an ink-jet printer”).
Generally, an ink-jet printer is advantageous in that it is low in cost and obtains high quality color printing, it can be easily obtained and has been widely propagated to general users as well as offices along with the propagation of personal computers, digital cameras and the like.
The ink-jet printer in general includes a movable body called a carriage integrally having an ink cartridge and a print head reciprocating across a print medium (the printing paper) in a direction perpendicular to a paper feed direction, and particulates of liquid ink from a nozzle of the print head are discharged (spread) into a dot shape to thereby draw predetermined characters and images on the print medium to create desired prints. The carriage has an ink cartridge of, for example, four (4) colors such as black, yellow, magenta and cyan, and thereby not only black-and-white printing but also full color printing by mixing each of the colors can be executed. (Moreover, 6-color printing, 7-color printing or 8-color printing has been practically used by adding light cyan or light magenta to the colors above.)
Furthermore, in the ink-jet printer which is configured to execute printing while the print head on the carriage reciprocates in a direction perpendicular to the paper feed direction, since the print head is required to reciprocate from tens of times to several hundreds of times or more so that the whole page may be finely printed, there is a problem in that it takes a longer time to perform the printing as compared with printing systems of other types such as, for example, a laser printer using electro-photographic technology used for a copying machine.
Correspondingly, in the ink-jet printer which does not use a carriage but instead disposes a print head equal to (or longer than) the width of the printing paper, since the print head is not required to move in the across-the-width direction of the printing paper and thereby printing can be executed through one scan (1 path or pass), it is possible to perform high-speed printing like the laser printer. Furthermore, since the carriage loaded with the print head and driver systems is not required, printer cases can be reduced in size and weight and thus there is an advantage in that noise can be considerably reduced. The ink-jet printer of the former type is generally called “a multi-pass-type printer” and the ink-jet printer of the latter type is generally called “a line head-type printer” or “a serial printer”.
However, since the print head that is indispensable to an ink-jet printer disposes minute nozzles approximately 10 to 70 μm in diameter in one row at regular intervals or in a plurality of rows in the printing direction, the ink discharging direction of some nozzles may be inclined or the position of the nozzles may be deviated from an ideal position, the impact position of the dot formed by the nozzle may be deviated from the ideal position, thereby, a “flight curve phenomenon” sometimes can occur. In addition, the irregularity occurs by a nozzle gap characteristic, thereby the ink amount may be too large or small, as compared with the ideal amount.
As a result, a bad printing, called the “banding (strip) phenomenon” occurs on a part printed by using the defective nozzles, and thereby the printing quality is often remarkably degraded. That is to say, if the “flight curve phenomenon” occurs, the distance between the dots discharged by the nozzles adjacent to each other becomes uneven, so that a “white strip” (in case that the printing paper is white) occurs on a part where the distance between the adjacent dots is larger than normal and a “dark strip” occurs on a part where the distance between the adjacent dots is smaller than normal. Furthermore, when the value of an ink amount is not an ideal value, “the dark strip” is shown in a nozzle part with a large amount of ink and “the white strip” is shown in a part with a small amount of ink.
The banding phenomenon occurs more frequently in “a line head-type printer” (serial printer) having a fixed print head or a print medium (1 pass printing) than in “a multi pass-type printer”. (There is a technology which reduces the ability to see the banding by forcing the print head to reciprocate several times in the multi-pass-type printer.)
Even though advances in the manufacturing technology of the print head and the design of the print head, that is, the R&D in hardware, is briskly progressing to prevent bad printing originated by the banding phenomenon, it is becoming difficult to provide a print head for which “the banding phenomenon” is completely resolved due to manufacturing costs, technology restraints and the like.
Consequently, there is concomitantly provided a technology to reduce “the banding phenomenon” using software techniques such as print control in addition to the improvement in hardware as shown above.
For example, as disclosed in JP-A-2002-19101 or JP-A-2003-136702, the gap of the head can be handled using a shading compensation technology for a part with low printing density, and the banding or the gap can be hidden by using and substituting other colors for a part with high printing density (for example, substituting cyan, magenta or the like in case of printing in black) in order to respond to the gap of a nozzle or the non-discharge of ink.
Furthermore, as disclosed in JP-A-2003-63043, in accordance with a beta image (that is, a fully painted image in which the base is not seen), there is provided a technique which generates the beta image with all of the nozzles by increasing an amount discharged from the nozzle adjacent to the neighboring pixel of the non-discharge nozzle.
In addition, as disclosed in JP-A-5-30361, the variation amount of each nozzle is fed-back to the error diffusion and processed, and the gap in the amount of ink discharged is absorbed thereby the banding phenomenon is avoided.
Moreover, as disclosed in JP-A-2004-58284, if something is wrong with the ink discharging status of a nozzle (N), by adding recording data corresponding to the defective nozzle (N) to recording data corresponding to the neighboring nozzles (N−1) and (N+1) located adjacent to the defective nozzle (N), recording data corresponding to the defective nozzle (N) is compensated and thereby the banding phenomenon is avoided.
However, the techniques to cope with the banding phenomenon or the gap by using other colors like the conventional technologies disclosed in JP-A-2002-19101 and JP-A-2003-136702 shown above are not suitable for printing requiring a high resolution and a high quality as in color photo image printing, since the color of the processed part may be modified.
Furthermore, in case of the method of avoiding “the white strip” by distributing the information of the non-discharge nozzle to the right and left for the part with high density to “the flight curve phenomenon” described above, the white strip may be reduced, but a problem is found in that the banding still remains.
Moreover, in the conventional technologies disclosed in JP-A-2003-63043 shown above, if the prints are a beta image, the method can be used, but if the prints are in a medium gradation (half tone), the method cannot be used. Furthermore, for a thin line, in the method of using another color which is infrequently used, there is no choice but for the image to include a part with a changed color.
In addition, in the method disclosed in JP-A-5-30361, in accordance with a problem that the dot-forming is varied, the process to perform a proper feed-back is complicated, whereby it is difficult to resolve the problem.
Moreover, in the method disclosed in JP-A-2004-58284 as shown above, for the processing after the density value is 2, when a dot of a different size is formed by a neighboring nozzle, if the dot has a γ characteristic, a problem is found in that there is a risk that the area gradation of the part is broken.